1. Field of the Invention
The present invention relates to a projection screen, and, more particularly, to a symmetrical projection screen having screen surfaces constructed in a front-and-rear symmetrical structure, whereby the flatness of the screen is considerably improved.
2. Description of the Related Art
The flatness of a screen is one of the most important factors of the screen.
Specifically, when the screen is not flat, a wave and wrinkle phenomenon occurs on the screen, and therefore, an image may be nonuniformly displayed on the screen. Especially in the case of a reflection type screen having high reflexibility, the wave and wrinkle phenomenon is deepened, and therefore, the normal use of the screen is not possible.
According to circumstances, a plurality of screen units 4 may be transported while being separated from each other, and then may be assembled in a site to construct a large-sized screen.
In this case, the screen units 4 may be incorrectly assembled due to the change in the weather, the transportation environment, and the assembly method.
When the screen units 4 are vertically assembled in a two-stage structure, the lower screen unit 4 may be deformed due to the weight of the upper screen unit 4.
In the case of a roll screen as shown in FIG. 3, the screen is unrolled downward when in use, and the screen is rolled upward when in safekeeping. As the rolling and unrolling operation of the screen is repeatedly carried out, and seasons or weathers are changed, however, the left and right sides of the screen shrink inward (a concave phenomenon), and the surface of the screen is wrinkled in the form of waves (a wave phenomenon).